The present invention relates to an improvement in a continuous microorganism cultivating apparatus.
In producing a useful material using a continuous microorganism cultivating apparatus which utilizes a metabolic function of microorganisms, it is necessary not only to maintain the concentration of microorganisms (microbes) in a reaction vessel at a high level but also removes metabolic products which will impede the growth of the microbes, in order to improve productivity.
As methods for maintaining the microbial concentration at a high level there are known, for example, a method in which microbes are precipitated and agglutinated, and a method in which microbes are immobilized. However, these methods are often impractical because a long time is required.
In view of this impracticality in the prior art, filters have been used for separating microbes and a metabolic product from each other continuously over a relatively short time. Examples of such filters include sintered tungsten tubes, unglazed ceramic supports coated with diatomaceous earth, and hollow fibers made of a synthetic resin. The problems with these filters are whether they are durable, stable over a long period, or re-employable. Particularly, it is questionable whether these filters can be back washed for avoiding plugging up of the filters by microbes or whether they can be cleaned by heat sterilization for reuse.
On this regard, a sintered tungsten tube is easily corroded by acid and is not suitable for back wash. In the case of a filter constituting by a ceramic support coated with diatomaceous earth, it is impossible to effect back washing, since the ceramic material serving as the support is coarse, having a pore diameter in the range of 10 to 50 .mu.m. This is because the ceramic material need not have a separating function. Further, a hollow fiber made of a synthetic resin does not permit back wash or heat sterilization and permits only a small treatment volume.